Optimine
This mod improves FPS, especially for slower computers. Gains of 20FPS and more are common.

Sound Mod Enabler
Allows you to use custom sounds.

Pluckin' Crazy
This mod allows you to utilize a right-click function on Chicken mobs, causing them to drop feathers each time. When all the feathers are plucked, the Chicken dies. Upon death, the Chicken drops feathers or eggs. The addition of egg drops is also useful for mods that use them in recipes!

Prefix Skeletons
Enables skeletons to use 303's custom arrows. Every skeleton has a randomly selected prefix like Normal, Fire, Explosive, Ice, etc., which determines the arrows it shoots. Skeletons hold their prefix arrow in hand and drop it upon death.

Minimap Mod
Shows a minimap in the corner of the screen with configurable waypoints and other options. Useful if you always get lost.

Single Player Commands
This mod introduces commands to singleplayer!

Death Chest Beta 1.2
When you die, if you have a chest in your inventory, it will be placed where you die, or in the closest available spot. The chest will be filled with as many items as possible. Items stored in the crafting slot are still lost, as usual, and any excess that won't fit in the chest will be dropped.

Fast Building
Allows you to quickly place blocks in rows from an item stack

Terrain Tweaker SMP Mod
The mod tweaks the settings in the terrain generator allowing for things like mostly flooded worlds,

having the new Nexus blocks mineable in the real world, Muddy swamps etc. Achieved via some simple additions to your server.properties file.

Enhanced Compass Mod
Allows you to make the compass point towards your spawn point, North, or both. The needle color is customizable.

Transmutation
Adds 17 recipes that allow you to transmute materials.

Giant Head Cheat Code: The Mod
Makes all heads in the game bigger.

Flint Crafting
Allows you to craft flint with three gravel.

Server Browser
Adds five favorites buttons to the multiplayer option, allowing you to favorite servers.

MyCraft Mod Manager
A mod manager similar to ModLoader that will work on any minecraft version. Includes smooth lighting, flying, proxy and modding API. Compatible with ModLoader mods.

ModLoader
A mod, kind of like a mod manager, that stops conflicts with mods that alter rendering, recipes, add entities, gui, smeltables or fuel. If you're a modder, feel free to decompile this and learn how to make mods work with it. Support for 303's modifications is included. In addition, texture packs are supported for override images and chunk population hook was added.

Scroll the Sky
While holding left control, you can change the time with the mouse wheel, or K and L. Special version lets you speed up and slow down time.

Stop Resizing UI v 0.2
This little tweak stops the resizing of the UI when you maximize or make the MineCraft window bigger.